Water permeability and its activation energy of fertilized and unfertilized mouse ova.

A photomicroscopic method has been used to determine the kinetics of water loss at various constant temperatures from fertilized and unfertilized mouse ova. Ova were transferred into hypertonic saline solutions, photographed, and their volumes calculated from their cross-sectional areas as a function of time after transfer. Curves describing the observed water loss have been compared to those calculated using a programmed version of the classical water permeability equation. The hydraulic conductivity, Lp, was determined by changing its value in the calculation until the majority of the observed cell volumes fell on or very close to the calculated curve of volume vs. time. In this way, fertilized and unfertilized ova were found to have respective hydraulic conductivities of 0.43 and 0.44 micron 3/micron 2-min-atm at 20 degrees C and respective activation energies for water permeability of 13.0 and 14.5 kcal/mol.